A toxicokinetic study to elucidate 3-hydroxybenzo(a)pyrene atypical urinary excretion profile following intravenous injection of benzo(a)pyrene in rats

Comparison of urinary 3-hydroxybenzo(a)Pyrene (3-OHBaP) and trans-anti-7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo(a)Pyrene (TetraolBaP) as biomarkers of exposure to carcinogenic BaP

INTRODUCTION

Biomonitoring of exposure to carcinogenic Benzo(a)Pyrene is generally based on measurement of urinary 3-hydroxybenzo(a)pyrene (3-OHBaP), but its analysis is complex and only reflects the BaP detoxification pathway. TetraolBaP, another BaP metabolite resulting from the metabolic activation pathway, is now available but has not yet been studied in occupational settings or compared with 3-OHBaP.

METHODS

Biomonitoring was carried out on 118 subjects working in the aluminium smelting industry. 3 urine samples were collected from each subject at the beginning and end of the working week. Pyrene metabolite (1-hydroxypyrene) and the two BaP biomarkers (3-OHBaP and TetraolBaP) were analysed using LC-Fluorescence and GC-NCI-MS-MS.

RESULTS

The workers studied were found to be highly exposed, with 1-OHP and 3-OHBaP frequently exceeding maximum recommended values in occupational settings. Maximum concentrations were measured at end of shift+16h for all biomarkers, highlighting dermal exposure and/or temporary storage. Correlations were strong between 1-OHP and 3-OHBaP (r = 0.68-0.75) as well as between 3-OHBaP and TetraolBaP (r = 0.67-0.78), and moderate between 1-OHP and TetraolBaP (r = 0.59-0.76). While TetraolBaP levels were higher at low PAH exposures, TetraolBaP increased much more slowly at high exposures, indicating progressive saturation of the bioactivation pathway. The [3-OHBaP]/[TetraolBaP] ratio was found to be significantly lower in chronically exposed workers. Urinary TetraolBaP levels corresponding to 1-OHP (2.5 μg/L or 1 μmol/mol creatinine) or 3-OHBaP (0.4 nmol/mol creatinine) guidance values were found to range between 0.84 and 0.95 nmol/mol creatinine.

CONCLUSIONS

TetraolBaP, resulting from carcinogenic BaP's metabolic activation pathway, was shown to be a diagnostically specific and sensitive biomarker for determining subjects' toxic internal exposure to PAHs in different contexts (occupational settings, environment) and assessing health risks.

Biomarkers for polycyclic aromatic hydrocarbons in human excreta: recent advances in analytical techniques-a review

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants that are generated by the incomplete combustion of organic materials. The main anthropogenic sources of PAHs are the combustion of solid fuels for heating purposes, illegal waste incineration, road transport and industries based on fossil fuels. PAHs can easily enter the body because they are present in all elements of the environment, including water, soil, air, and food. Due to their ubiquitous presence, PAHs, may exert a harmful effect on human health. Assessing PAH exposure through biomonitoring mostly involve techniques to measure the concentration of 1-hydroxypyrene in human urine. Nevertheless, through recent progress in analytical techniques, other common metabolites of PAHs in human biospecimens can be detected. A scientific literature search was conducted to determine which hydroxy derivatives of PAHs are markers of PAHs exposure and to reveal the leading sources of these compounds. Techniques for analyzing biological samples to identify OH-PAHs are also discussed. The most frequently determined OH-PAH in human urine is 1-hydroxypyrene, the concentration of which reaches up to a dozen ng/L in urine. Apart from this compound, the most frequently determined biomarkers were naphthalene and fluorene metabolites. The highest concentrations of 1- and 2-hydroxynaphthalene, as well as 2-hydroxyfluorene, are associated with occupational exposure and reach approximately 30 ng/L in urine. High molecular weight PAH metabolites have been identified in only a few studies. To date, PAH metabolites in feces have been analyzed only in animal models for PAH exposure. The most frequently used analytical method is HPLC-FLD. However, compared to liquid chromatography, the LOD for gas chromatography methods is at least one order of magnitude lower. The hydroxy derivatives naphthalene and fluorene may also serve as indicators of PAH exposure.

Biomonitoring of firefighting forces: a review on biomarkers of exposure to health-relevant pollutants released from fires

Occupational exposure as a firefighter has recently been classified as a carcinogen to humans by International Agency for Research on Cancer (IARC). Biomonitoring has been increasingly used to characterize exposure of firefighting forces to contaminants. However, available data are dispersed and information on the most relevant and promising biomarkers in this context of firefighting is missing. This review presents a comprehensive summary and critical appraisal of existing biomarkers of exposure including volatile organic compounds such as polycyclic aromatic hydrocarbons, several other persistent other organic pollutants as well as heavy metals and metalloids detected in biological fluids of firefighters attending different fire scenarios. Urine was the most characterized matrix, followed by blood. Firefighters exhaled breath and saliva were poorly evaluated. Overall, biological levels of compounds were predominantly increased in firefighters after participation in firefighting activities. Biomonitoring studies combining different biomarkers of exposure and of effect are currently limited but exploratory findings are of high interest. However, biomonitoring still has some unresolved major limitations since reference or recommended values are not yet established for most biomarkers. In addition, half-lives values for most of the biomarkers have thus far not been defined, which significantly hampers the design of studies. These limitations need to be tackled urgently to improve risk assessment and support implementation of better more effective preventive strategies.

Metabolism of benzo[a]pyrene after low-dose subchronic exposure to an industrial mixture of carcinogenic polycyclic aromatic hydrocarbons in rats: a cocktail effect study

Polycyclic aromatic hydrocarbons (PAHs) are interesting environmental pollutants for understanding cocktail effects. High-molecular-weight-PAHs (HMW-PAHs) are classified as probable or possible carcinogens; only benzo[a]pyrene (B[a]P) is a certain carcinogen in humans. Their toxicity depends on their metabolic activation. While 3-hydroxybenzo[a]pyrene (3-OHB[a]P) represents its detoxification pathway, trans-anti-7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (tetrol-B[a]P) represents the carcinogenicity pathway. The objective was to study the metabolism of B[a]P and HMW-PAHs during chronic low-dose exposure to B[a]P or a PAH mixture. Rats were exposed orally 5 times/week for 10 weeks to low-levels of B[a]P (0.02 and 0.2 mg.kg^-1.d^-1) or to an industrial mixture extracted from coal tar pitch (CTP) adjusted to 0.2 mg.kg^-1.d^-1 B[a]P. Urinary levels of monohydroxy-, diol-, and tetrol-PAH were measured during weeks 1 and 10 by HPLC-fluorescence and GC‒MS/MS. After 1 week, the percentages of B[a]P eliminated as 3-OHB[a]P and tetrol-B[a]P were not different depending on the dose of B[a]P, whereas they were reduced by half in the CTP group. Repeated exposure led to an increase in the percentages of the 2 metabolites for the 0.02-B[a]P group. Moreover, the percentage of B[a]P eliminated as 3-OHB[a]P was equal in the 0.2-B[a]P and CTP groups, whereas it remained halved for tetrol-B[a]P in the CTP group. The percent elimination of HMW-PAH metabolites did not vary between weeks 1 and 10. Thus, dose, duration of exposure and chemical composition of the mixture have a major influence on PAH metabolism that goes beyond a simple additive effect. This work contributes to the reflection on determination of limit values and risk assessments in a context of poly-exposures.

Human Biomonitoring of Selected Hazardous Compounds in Portugal: Part I-Lessons Learned on Polycyclic Aromatic Hydrocarbons, Metals, Metalloids, and Pesticides

Human biomonitoring (HBM) data provide information on total exposure regardless of the route and sources of exposure. HBM studies have been applied to quantify human exposure to contaminants and environmental/occupational pollutants by determining the parent compounds, their metabolites or even their reaction products in biological matrices. HBM studies performed among the Portuguese population are disperse and limited. To overcome this knowledge gap, this review gathers, for the first time, the published Portuguese HBM information concerning polycyclic aromatic hydrocarbons (PAHs), metals, metalloids, and pesticides concentrations detected in the urine, serum, milk, hair, and nails of different groups of the Portuguese population. This integrative insight of available HBM data allows the analysis of the main determinants and patterns of exposure of the Portuguese population to these selected hazardous compounds, as well as assessment of the potential health risks. Identification of the main difficulties and challenges of HBM through analysis of the enrolled studies was also an aim. Ultimately, this study aimed to support national and European policies promoting human health and summarizes the most important outcomes and lessons learned through the HBM studies carried out in Portugal.

Predicting the in vivo developmental toxicity of benzo[a]pyrene (BaP) in rats by an in vitro-in silico approach

Developmental toxicity testing is an animal-intensive endpoints in toxicity testing and calls for animal-free alternatives. Previous studies showed the applicability of an in vitro–in silico approach for predicting developmental toxicity of a range of compounds, based on data from the mouse embryonic stem cell test (EST) combined with physiologically based kinetic (PBK) modelling facilitated reverse dosimetry. In the current study, the use of this approach for predicting developmental toxicity of polycyclic aromatic hydrocarbons (PAHs) was evaluated, using benzo[a]pyrene (BaP) as a model compound. A rat PBK model of BaP was developed to simulate the kinetics of its main metabolite 3-hydroxybenzo[a]pyrene (3-OHBaP), shown previously to be responsible for the developmental toxicity of BaP. Comparison to in vivo kinetic data showed that the model adequately predicted BaP and 3-OHBaP blood concentrations in the rat. Using this PBK model and reverse dosimetry, a concentration–response curve for 3-OHBaP obtained in the EST was translated into an in vivo dose–response curve for developmental toxicity of BaP in rats upon single or repeated dose exposure. The predicted half maximal effect doses (ED₅₀) amounted to 67 and 45 mg/kg bw being comparable to the ED₅₀ derived from the in vivo dose–response data reported for BaP in the literature, of 29 mg/kg bw. The present study provides a proof of principle of applying this in vitro–in silico approach for evaluating developmental toxicity of BaP and may provide a promising strategy for predicting the developmental toxicity of related PAHs, without the need for extensive animal testing.

Grill Workers Exposure to Polycyclic Aromatic Hydrocarbons: Levels and Excretion Profiles of the Urinary Biomarkers

Grilling activities release large amounts of hazardous pollutants, but information on restaurant grill workers’ exposure to polycyclic aromatic hydrocarbons (PAHs) is almost inexistent. This study assessed the impact of grilling emissions on total workers’ exposure to PAHs by evaluating the concentrations of six urinary biomarkers of exposure (OHPAHs): naphthalene, acenaphthene, fluorene, phenanthrene, pyrene, and benzo(a)pyrene. Individual levels and excretion profiles of urinary OHPAHs were determined during working and nonworking periods. Urinary OHPAHs were quantified by high-performance liquid-chromatography with fluorescence detection. Levels of total OHPAHs (∑OHPAHs) were significantly increased (about nine times; p ≤ 0.001) during working comparatively with nonworking days. Urinary 1-hydroxynaphthalene + 1-hydroxyacenapthene and 2-hydroxyfluorene presented the highest increments (ca. 23- and 6-fold increase, respectively), followed by 1-hydroxyphenanthrene (ca. 2.3 times) and 1-hydroxypyrene (ca. 1.8 times). Additionally, 1-hydroxypyrene levels were higher than the benchmark, 0.5 µmol/mol creatinine, in 5% of exposed workers. Moreover, 3-hydroxybenzo(a)pyrene, biomarker of exposure to carcinogenic PAHs, was detected in 13% of exposed workers. Individual excretion profiles showed a cumulative increase in ∑OHPAHs during consecutive working days. A principal component analysis model partially discriminated workers’ exposure during working and nonworking periods showing the impact of grilling activities. Urinary OHPAHs were increased in grill workers during working days.

Early markers of cardiovascular disease are associated with occupational exposure to polycyclic aromatic hydrocarbons

Occupational exposure to soot, rich in polycyclic aromatic hydrocarbons (PAH), has been associated with increased risk of cardiovascular disease (CVD). However, our knowledge about PAH exposure and early markers of CVD remains limited. In this cross-sectional study of 151 chimney sweeps and 152 controls, we investigated occupational exposure to PAH and early markers of CVD. Blood pressure (BP) (chimney sweeps only), urinary PAH metabolites and serum biomarkers were measured (C-reactive protein, homocysteine, gamma-glutamyltransferase, cholesterol, HDL, LDL, and triglycerides). Chimney sweeps had up to 7 times higher concentrations of PAH metabolites in urine than controls (P < 0.001): median concentrations (adjusted for specific gravity) for 1-hydroxypyrene, 2-hydroxyphenanthrene, 3-hydroxybenzo[a]pyrene, and 3-hydroxybenzo[a]anthracene were 0.56 µg/L, 0.78 µg/L, 4.75 ng/L, and 6.28 ng/L, respectively. Compared with controls, chimney sweeps had increased homocysteine, cholesterol, and HDL (β = 3.4 µmol/L, 0.43 mmol/L, and 0.13 mmol/L, respectively, P ≤ 0.003, adjusted for age, BMI, and smoking). In chimney sweeps, PAH metabolites correlated positively with the percentage of soot sweeping (P < 0.001). 2-hydroxyphenanthrene, 3-hydroxybenzo[a]pyrene, and 3-hydroxybenzo[a]anthracene were positively associated with diastolic BP (P < 0.044, adjusted for age, BMI, and smoking). PAH exposure among chimney sweeps resulted in elevated levels of markers for CVD risk. These findings stress the need to reduce occupational exposure to PAH.

Urinary Metabolites of Polycyclic Aromatic Hydrocarbons and the Association with Lipid Peroxidation: A Biomarker-Based Study between Los Angeles and Beijing

Air pollution is among the top threats to human health in China. As air toxicants, polycyclic aromatic hydrocarbons (PAHs) could bring significant risks to population; however, the exposure to PAHs in China and its health impact are not fully understood. In 2012, a summer exchange program allowed 10 students to travel from Los Angeles to Beijing and stay there for 10 weeks. Based on the program, this study investigated the difference in urinary concentration of 12 hydroxylated-PAHs (Σ12OH-PAHs) and malondialdehyde (MDA) between the two cities. The median concentration of Σ12OH-PAHs in Beijing (14.1 μg g(-1) creatinine) was significantly higher than that in Los Angeles (5.78 μg g(-1) creatinine), indicating a higher exposure in Beijing. The ratios of homogeneous OH-PAHs (e.g., 1-/2-OH-NAP) changed significantly between the two cities (p < 0.01), which might suggest a potential alteration in metabolism subsequent to exposure. A significant association between Σ12OH-PAHs and MDA (p < 0.01) was observed, with the association varying between the two cities. This study suggests that exposure to PAHs might be linked to metabolism alteration and calls for future studies to investigate the role this possible alteration played in the health effects of PAHs exposure.

Comparison of toxicogenomics and traditional approaches to inform mode of action and points of departure in human health risk assessment of benzo[a]pyrene in drinking water

Toxicogenomics is proposed to be a useful tool in human health risk assessment. However, a systematic comparison of traditional risk assessment approaches with those applying toxicogenomics has never been done. We conducted a case study to evaluate the utility of toxicogenomics in the risk assessment of benzo[a]pyrene (BaP), a well-studied carcinogen, for drinking water exposures. Our study was intended to compare methodologies, not to evaluate drinking water safety. We compared traditional (RA1), genomics-informed (RA2) and genomics-only (RA3) approaches. RA2 and RA3 applied toxicogenomics data from human cell cultures and mice exposed to BaP to determine if these data could provide insight into BaP's mode of action (MOA) and derive tissue-specific points of departure (POD). Our global gene expression analysis supported that BaP is genotoxic in mice and allowed the development of a detailed MOA. Toxicogenomics analysis in human lymphoblastoid TK6 cells demonstrated a high degree of consistency in perturbed pathways with animal tissues. Quantitatively, the PODs for traditional and transcriptional approaches were similar (liver 1.2 vs. 1.0 mg/kg-bw/day; lungs 0.8 vs. 3.7 mg/kg-bw/day; forestomach 0.5 vs. 7.4 mg/kg-bw/day). RA3, which applied toxicogenomics in the absence of apical toxicology data, demonstrates that this approach provides useful information in data-poor situations. Overall, our study supports the use of toxicogenomics as a relatively fast and cost-effective tool for hazard identification, preliminary evaluation of potential carcinogens, and carcinogenic potency, in addition to identifying current limitations and practical questions for future work.

Single cell gel electrophoresis (SCGE) and Pig-a mutation assay in vivo-tools for genotoxicity testing from a regulatory perspective: a study of benzo[a]pyrene in Ogg1(-/-) mice

The OECD has developed test guidelines (TG) to identify agents with genotoxic effects. The in vivo alkaline single cell gel electrophoresis (SCGE) assay is currently being prepared to become such a TG. The performance of a combined SCGE/Pig-a gene mutation study was evaluated with the prototypical genotoxicant benzo[a]pyrene (BaP) at an exposure level known to induce germ cell mutation. We aimed to better understand (i) the strengths and weaknesses of the two methods applied in blood and their potential to predict germ cell mutagenicity, and (ii) the involvement of reactive oxygen species (ROS) following in vivo BaP-exposure. To explore the involvement of ROS on BaP genotoxicity, we utilised a mouse model deficient in a DNA glycosylase. Specifically, C57BL/6 mice (Ogg1(+/+) and Ogg1(-/-)) were treated for three consecutive days with 50 mg BaP/kg/day. DNA damage in nucleated blood cells was measured four hours after the last treatment with the SCGE assay, with and without formamidopyrimidine DNA glycosylase (Fpg). Pig-a mutant phenotype blood erythrocytes were analysed two and four weeks after treatment. BaP-induced DNA lesions were not significantly increased in either version of the SCGE assay. The phenotypic mutation frequencies for immature and mature erythrocytes were significantly increased after two weeks. These effects were not affected by genotype, suggesting oxidative damage may have a minor role in BaP genotoxicity, at least in the acute exposure situation studied here. While both assays are promising tools for risk assessment, these results highlight the necessity of understanding the limitations regarding each assay's ability to detect chemicals' genotoxic potential.

Use of physiologically-based pharmacokinetic modeling to simulate the profiles of 3-hydroxybenzo(a)pyrene in workers exposed to polycyclic aromatic hydrocarbons

Biomathematical modeling has become an important tool to assess xenobiotic exposure in humans. In the present study, we have used a human physiologically-based pharmacokinetic (PBPK) model and an simple compartmental toxicokinetic model of benzo(a)pyrene (BaP) kinetics and its 3-hydroxybenzo(a)pyrene (3-OHBaP) metabolite to reproduce the time-course of this biomarker of exposure in the urine of industrially exposed workers and in turn predict the most plausible exposure scenarios. The models were constructed from in vivo experimental data in rats and then extrapolated from animals to humans after assessing and adjusting the most sensitive model parameters as well as species specific physiological parameters. Repeated urinary voids from workers exposed to polycyclic aromatic hydrocarbons (PAHs) have been collected over the course of a typical workweek and during subsequent days off work; urinary concentrations of 3-OHBaP were then determined. Based on the information obtained for each worker (BaP air concentration, daily shift hours, tasks, protective equipment), the time courses of 3-OHBaP in the urine of the different workers have been simulated using the PBPK and toxicokinetic models, considering the various possible exposure routes, oral, dermal and inhalation. Both models were equally able to closely reproduce the observed time course of 3-OHBaP in the urine of workers and predicted similar exposure scenarios. Simulations of various scenarios suggest that the workers under study were exposed mainly by the dermal route. Comparison of measured air concentration levels of BaP with simulated values needed to obtain a good approximation of observed time course further pointed out that inhalation was not the main route of exposure for most of the studied workers. Both kinetic models appear as a useful tool to interpret biomonitoring data of PAH exposure on the basis of 3-OHBaP levels.

Relevance of urinary 3-hydroxybenzo(a)pyrene and 1-hydroxypyrene to assess exposure to carcinogenic polycyclic aromatic hydrocarbon mixtures in metallurgy workers

OBJECTIVES

In metallurgy, workers are exposed to mixtures of polycyclic aromatic hydrocarbons (PAHs) in which some compounds are carcinogenic. Biomonitoring of PAH exposure has been performed by measuring urinary 1-hydroxypyrene (1-OHP), a metabolite of pyrene which is not carcinogenic. This study investigated the use of 3-hydroxybenzo(a)pyrene (3-OHBaP), a metabolite of benzo(a)pyrene (BaP) which is the main carcinogenic component in PAHs, to improve carcinogen exposure assessment.

METHODS

We included 129 metallurgy workers routinely exposed to PAHs during working hours. Urinary samples were collected at three sampling times at the beginning and at the end of the working week for 1-OHP and 3-OHBaP analyses.

RESULTS

Workers in anode production showed greater exposure to both biomarkers than those in cathode or silicon production, with respectively, 71, 40, and 30% of 3-OHBaP concentrations exceeding the value of 0.4 nmol mol(-1) creatinine. No difference was observed between the 3-OHBaP levels found at the end of the penultimate workday shift and those at the beginning of the last workday shift. Within these plants, the 1-OHP/3-OHBaP ratios varied greatly according to the workers' activity and emission sources. Using linear regression between these two metabolites, the 1-OHP level corresponding to the guidance value for 3-OHBaP ranged from 0.7 to 2.4 µmol mol(-1) creatinine, depending on the industrial sector.

CONCLUSIONS

This study emphasizes the interest of monitoring urinary 3-OHBaP at the end of the last workday shift when working week exposure is relatively steady, and the irrelevance of a single guideline value for 1-OHP when assessing occupational health risk.

Understanding the linked kinetics of benzo(a)pyrene and 3-hydroxybenzo(a)pyrene biomarker of exposure using physiologically-based pharmacokinetic modelling in rats

3-hydroxybenzo(a)pyrene (3-OHBaP) in urine has been proposed as a biomarker of occupational exposure to polycyclic aromatic hydrocarbons. However, to reconstruct exposure doses in workers from biomarker measurements, a thorough knowledge of the kinetics of the benzo(a)pyrene (BaP) and 3-OHBaP given different routes of exposure is needed. A rat physiologically-based pharmacokinetic model of BaP and 3-OHBaP was built. Organs (tissues) represented as compartments were based on in vivo experimental data in rats. Tissue: blood partition coefficients, permeability coefficients, metabolism rates, excretion parameters, and absorption fractions and rates for different routes-of-entry were obtained directly from published in vivo time courses of BaP and 3-OHBaP in blood, various tissues and excreta of rats. The latter parameter values were best-fitted by least square procedures and Monte Carlo simulations. Sensitivity analyses were then carried out to ensure the stability of the model and the key parameters driving the overall modeled kinetics. This modeling pointed out critical determinants of the kinetics: (1) hepatic metabolism of BaP and 3-OHBaP elimination rate as the most sensitive parameters; (2) the strong partition of BaP in lungs compared to other tissues, followed by adipose tissues and liver; (3) the strong partition of 3-OHBaP in kidneys; (4) diffusion-limited tissue transfers of BaP in lungs and 3-OHBaP in lungs, adipose tissues and kidneys; (5) significant entero-hepatic recycling of 3-OHBaP. Very good fits to various sets of experimental data in rats from four different routes-of-entry (intravenous, oral, dermal and inhalation) were obtained with the model.

Large prospective investigation of meat intake, related mutagens, and risk of renal cell carcinoma

BACKGROUND

The evidence for meat intake and renal cell carcinoma (RCC) risk is inconsistent. Mutagens related to meat cooking and processing, and variation by RCC subtype may be important to consider.

OBJECTIVE

In a large US cohort, we prospectively investigated intake of meat and meat-related compounds in relation to risk of RCC, as well as clear cell and papillary RCC histologic subtypes.

DESIGN

Study participants (492,186) completed a detailed dietary assessment linked to a database of heme iron, heterocyclic amines (HCA), polycyclic aromatic hydrocarbons (PAHs), nitrate, and nitrite concentrations in cooked and processed meats. Over 9 (mean) y of follow-up, we identified 1814 cases of RCC (498 clear cell and 115 papillary adenocarcinomas). HRs and 95% CIs were estimated within quintiles by using multivariable Cox proportional hazards regression.

RESULTS

Red meat intake [62.7 g (quintile 5) compared with 9.8 g (quintile 1) per 1000 kcal (median)] was associated with a tendency toward an increased risk of RCC [HR: 1.19; 95% CI: 1.01, 1.40; P-trend = 0.06] and a 2-fold increased risk of papillary RCC [P-trend = 0.002]. Intakes of benzo(a)pyrene (BaP), a marker of PAHs, and 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP), an HCA, were associated with a significant 20-30% elevated risk of RCC and a 2-fold increased risk of papillary RCC. No associations were observed for the clear cell subtype.

CONCLUSIONS

Red meat intake may increase the risk of RCC through mechanisms related to the cooking compounds BaP and PhIP. Our findings for RCC appeared to be driven by strong associations with the rarer papillary histologic variant. This study is registered at clinicaltrials.gov as NCT00340015.

Meat-cooking mutagens and risk of renal cell carcinoma

BACKGROUND

High-temperature cooked meat contains two families of carcinogens, heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Given the kidneys' role in metabolism and urinary excretion of these compounds, we investigated meat-derived mutagens, as well as meat intake and cooking methods, in a population-based case-control study conducted in metropolitan Detroit and Chicago.

METHODS

Newly diagnosed, histologically confirmed adenocarcinoma of the renal parenchyma (renal cell carcinoma (RCC)) cases (n=1192) were frequency matched on age, sex, and race to controls (n=1175). The interviewer-administered Diet History Questionnaire (DHQ) included queries for meat-cooking methods and doneness with photographic aids. Levels of meat mutagens were estimated using the DHQ in conjunction with the CHARRED database.

RESULTS

The risk of RCC increased with intake of barbecued meat (P(trend)=0.04) and the PAH, benzo(a)pyrene (BaP) (multivariable-adjusted odds ratio and 95% confidence interval, highest vs lowest quartile: 1.50 (1.14, 1.95), P(trend)=0.001). With increasing BaP intake, the risk of RCC was more than twofold in African Americans and current smokers (P(interaction)<0.05). We found no association for HCAs or overall meat intake.

CONCLUSION

BaP intake, a PAH in barbecued meat, was positively associated with RCC. These biologically plausible findings advocate further epidemiological investigation into dietary intake of BaP and risk of RCC.

Evaluation of DNA adducts, DNA and RNA oxidative lesions, and 3-hydroxybenzo(a)pyrene as biomarkers of DNA damage in lung following intravenous injection of the parent compound in rats

Biomarkers of exposure and effect were assessed in 40 male Sprague-Dawley rats injected intravenously with 40 micromol/kg of benzo(a)pyrene (BaP) to determine which biomarkers are more representative of BaP-induced DNA damage in lung. Lung, liver, blood, and urine were collected at t = 2, 4, 8, 16, 24, 33, 48, 72, and 360 h postdosing. Specific BaP-diol epoxide (BPDE)-DNA adducts, 8-hydroxy-7,8-dihydro-2'-deoxyguanosine (8-OHdGuo), were measured in lung, liver, and mononucleated blood cells by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). Urinary 8-OHdGuo and 8-hydroxy-7,8-dihydroguanosine (8-OHGuo) were also determined by HPLC-MS/MS, and urinary 3-hydroxybenzo(a)pyrene was measured by HPLC/fluorescence. Between 2 and 72 h postdosing, BPDE-DNA adducts were significantly increased in lung, liver, and mononucleated blood cells of BaP-treated rats as compared to controls, with the highest levels found in lung. 8-OHdGuo levels also increased in lung of BaP-treated rats with values reaching statistical significance at 2, 8, and 16 h postinjection. No influence of BaP treatment was found on 8-OHdGuo and 8-OHGuo urinary excretions. BPDE-DNA adducts in lung were strongly correlated to urinary 3-OHBaP (r = 0.936 and p < 0.001) and to a lesser extent to blood BPDE-DNA adducts (r = 0.636 and p < 0.001), the latter of which were correlated to each other (r = 0.573 and p = 0.002). Urinary 3-OHBaP and BPDE-DNA adducts in mononucleated blood cells appear as relevant biomarkers of BaP genotoxic exposure and are highly promising for health risk assessment in humans.